The present invention relates to a transmitter arrangement for cylinder identification in an internal combustion engine having n cylinders.
It is known that in a four-stroke internal combustion engine the crankshaft rotates twice per working cycle and thus sweeps out an angle of 720 degrees before a specific cylinder re-assumes the same working position. In order to detect the instantaneous position of a cylinder, it is therefore not sufficient to determine the angular position of the crankshaft within a revolution; it must be detected, rather, whether the internal combustion engine is currently in the first or in the second half of the working cycle, corresponding to the first or second crankshaft revolution.
For this purpose, it is known from EP 0,371,158, for example, to provide in addition to a crankshaft transmitter a static camshaft transmitter as well, the periodic output signal of which consists of two distinguishable component signals which extend in an alternating fashion over one full crankshaft revolution in each case. A crankshaft transmitter additionally supplies a reference signal per crankshaft, by means of which a known angular position, the synchronisation position, is determined. Only after identification of the reference pulse is the position of the cylinder of the internal combustion engine accurately known in conjunction with the camshaft signal, and synchronisation of the ignition or injection-can be performed.
It follows that after the start of the internal combustion engine it is possible in the most unfavourable case for a complete crankshaft revolution to pass until the synchronisation position is first reached. Since it is only possible after synchronisation to inject fuel into the individual cylinders correctly in the cycle, in order to avoid a prolonged starting phase due to lack of injection during the first crankshaft revolution a first cylinder group is determined in the known method, into which injection is firstly performed in conjunction with the evaluation of the first component signal of the camshaft transmitter after the start. After a change in signal of the signal supplied by the camshaft transmitter, injection is also performed into the second cylinder group.
The known method therefore displays a possibility of how the injection can be improved directly after the start of the internal combustion engine; a quicker cylinder identification is not achieved in the process, nor is it, indeed, mandatory in this case.
German Offenlegungsschrift 3,608,321 discloses a device for detecting the cylinder-specific crankshaft position of a four-stroke engine having a cylinder number n, in which a signal transmitter connected to the crankshaft is subdivided on the circumference into n/2 equally large signal marking sections with one identifying mark in each case, and a signal transmitter connected to the camshaft is subdivided into n/2 or n equally large signalling sections whose uniform divisions diverge from one another. Immediately after the engine has been started, a cylinder allocation of the crankshaft position can be performed by a pulse comparison of the two signal transmitters that is synchronised by means of the identifying marks. A disadvantage of this device consists in that the distance between similar angle mark edges of the camshaft transmitter is non-uniform, so that it is not suitable for use as a trigger mark; this is disadvantageous in particular when emergency running is to be realised in the event of a defective crankshaft transmitter.